Kate Upton has refused to be interviewed by a lawyer who was hired by the Special Committee of the Board Directors of Guess to investigate her claim Chief Creative Officer Paul Marciano sexually assaulted her.

Upton had said publicly she would cooperate with the Guess investigation, but then changed her position when she learned the law firm that was involved in the probe was Marciano’s personal law firm. She called it “smoke and mirrors” and a “PR stunt to impress shareholders.”

TMZ has learned the Special Committee hired Glaser and Glaser, a high-powered L.A. law firm that has no ties to Guess or Marciano, to conduct the investigation. Marciano’s personal firm is now out of the picture.

Our sources say attorney Patty Glaser contacted Upton’s lawyer and asked if Upton would now sit for an interview. We’re told Upton’s lawyer said his client would not do the interview with Glaser because some of the information in the probe was already gathered by Marciano’s law firm, so the investigation was tainted.

We’re told Glaser assured the lawyer she was the only one in charge of the investigation, she had no preconceptions and wanted to be fair to both sides. Her lawyer didn’t budge … at least not so far.

Upton has claimed Marciano grabbed her breasts and forcibly kissed her neck and face, among other things, during a photo shoot in 2010.